1. Field of the Invention
This invention relates to ion exchange intensification in lithium batteries by increasing the anode contact area with the electrolyte.
2. Description of the Prior Art
Lithium and some other electrochemical devices or batteries whether they be of the liquid or solid state type characteristically use anodes formed from layers of metal. In lithium batteries for example it is common to form the anode by depositing a foil of lithium onto a base foil of nickel or other metal.
Lithium is a very difficult material to work with, it must be kept from water, it can be highly toxic to those exposed to it, and it also has a low melting point and corrodes upon contact with the air.
It is known in the manufacture of plates for lead acid batteries to form a paste containing particles of lead and a carrier material. The lead composition is then applied to a grid and allowed to dry, which produces plates having cavities therein which increases the electrolyte contact area and improves performance. The manufacture of such plates is described in the publication entitled Lead Acid Batteries by Hans Bode, published by John Wiley & Sons, New York, N.Y. 1977, Pages 102-244. While plates having the described characteristics are produced by the paste method, this method can not be used with lithium due to its considerably different nature, and the required handling characteristics.
In the prior art approach to forming the anode of lithium batteries, lithium is extruded or rolled into thin sheets, which are then mechanically pressed against a base foil to form the anode. With the multi stage handling required it is difficult to prevent the lithium from becoming contaminated, and due to its inherent characteristics it is difficult to bond the lithium with the base foil so that the resultant product is often not satisfactory and separations may occur.
The surface of extruded or rolled lithium foil is relatively smooth and flat, and after fabrication various layers of electrolyte and cathode materials are deposited thereon to form an electrochemical cell or device, which can be of the type described in our prior U.S. Pat. No. 4,576,883.
During battery operation ions are exchanged between the electrolyte and the lithium layer of the anode in contact therewith. The ion exchange is limited by the contact area between the lithium foil and the electrolyte. While the advantages of lithium batteries are well known the difficulties in their manufacture and the cost/efficiency have limited their acceptance. The need exists for a better method of manufacturing the anodes, and a more efficient anode in terms of cost and performance.